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Answer to the Friday Puzzle…..

On Friday I posted this puzzle. You have a straight-sided glass of orange juice that is filled to the brim like this…..

…and would like to share it with a friend. You have no other drinking vessel, and nothing with which to measure the depth or content of the glass. How do you make sure that you both get a fair share?

If you have not tried to solve it, have a go now. For everyone else the answer is after the break.

You simply drink until the level of the liquid runs from the lip of the glass to the top of the opposite bottom rim, like this:

Then there will be exactly 50% left. Did you solve it? Any other answers?

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.

The ACTUAL real life way this is done to prevent spilling any juice and thereby causing argument is…
Put finger on where you reckon half way down is then invite friend to drink whichever “half” they think is bigger to establish which of you drinks first. Drink down to finger.

Fairly easy problem, I got it on my first guess. My second guess was “drink the entire glass, then pour another full glass for the other person”… followed by my third guess of “make paper cups out of spare printer paper”.

I was going to say each use the same size (1 each) large measuring spoons and take turns-tedious ,yes but more exact than the angled solution,but less elegant than others’ popsicle solution,theirs being the best.

I enjoy the fact that most people seem to have interpreted the “rule” of “fair share” as equal amounts… which is a normal reading of course… But not mandated by the proposition as writ.
So I particularly enjoy the solutions not so easy as some have said (based on the simple geometric solution) that address other aspects of the notion of Fair.